The present invention relates to a swash plate type variable displacement compressor.
Japanese Laid-Open Patent Publications No. 5-172052 and No. 52-131204 disclose conventional swash plate type variable displacement type compressors (hereinafter, referred to as compressors). The compressors include a suction chamber, a discharge chamber, a swash plate chamber, and a plurality of cylinder bores, which are formed in a housing. A drive shaft is rotationally supported in the housing. The swash plate chamber accommodates a swash plate, which is rotatable through rotation of the drive shaft. A link mechanism, which allows change of the inclination angle of the swash plate, is arranged between the drive shaft and the swash plate. The inclination angle is defined with respect to a line perpendicular to the rotation axis of the drive shaft. Each of the cylinder bores accommodates a piston in a reciprocal manner and thus forms a compression chamber. A conversion mechanism reciprocates each of the pistons in the associated one of the cylinder bores by the stroke corresponding to the inclination angle of the swash plate through rotation of the swash plate. An actuator is capable of changing the inclination angle of the swash plate and controlled by a control mechanism.
In the compressor disclosed in Japanese Laid-Open Patent Publications No. 5-172052, each cylinder bore is formed in a cylinder block, which forms part of the housing, and is formed by a front cylinder bore arranged in front of the swash plate and a rear cylinder bore arranged behind the swash plate. Each piston includes a front head, which reciprocates in the front cylinder bore, and a rear head, which is integral with the front head and reciprocates in the rear cylinder bore.
In this compressor, a pressure regulation chamber is formed in a rear housing member of the housing. In addition to the cylinder bores, a control pressure chamber is formed in a cylinder block and communicates with the pressure regulation chamber. The control pressure chamber is located on the same side as the rear cylinder bores, that is, at a position behind the swash plate. The actuator is arranged in the control pressure chamber, while being prevented from rotating integrally with the drive shaft. Specifically, the actuator has a non-rotational movable body that overlaps with a rear end portion of the drive shaft. The inner peripheral surface of the non-rotational movable body rotationally supports the rear end portion of the drive shaft. The non-rotational movable body is movable in the direction of the rotation axis of the drive shaft. The non-rotational movable body is slidable in the control pressure chamber through the outer peripheral surface of the non-rotational movable body and slides in the direction of the rotation axis of the drive shaft. The non-rotational movable body is restricted from sliding about the rotation axis of the drive shaft. A pressing spring, which urges the non-rotational movable body forward, is arranged in the control pressure chamber. The actuator has a movable body, which is joined to the swash plate and movable in the direction of the rotation axis of the drive shaft. A thrust bearing is arranged between the non-rotational movable body and the movable body. A pressure control valve, which changes the pressure in the control pressure chamber, is provided between the pressure regulation chamber and the discharge chamber. Through such change of the pressure in the control pressure chamber, the non-rotational movable body and the movable body are moved along the rotation axis.
The link mechanism has a movable body and a lug arm fixed to the drive shaft. The lug arm is located one side of the swash plate. The movable body has a first elongated hole, which extends in a direction perpendicular to the rotation axis of the drive shaft from the side corresponding to the outer periphery toward the rotation axis. Also, the lug arm has a second elongated hole, which extends in a direction perpendicular to the rotation axis of the drive shaft from the side corresponding to the outer periphery toward the rotation axis. The swash plate has a first arm, which is located on the rear surface and extends toward the rear cylinder bores, and a second arm, which is located on the front surface and extends toward the front cylinder bores. A first pin is passed through the first elongated hole to couple the swash plate and the movable body to each other. The first arm is supported to pivot relative to the movable body about the first pin. A second pin is passed through the second elongated hole to couple the swash plate and the lug arm to each other. The second arm is supported to pivot relative to the lug arm about the second pin. The first pin and the second pin extend to be parallel with each other. By being passed through the first and second elongated holes, respectively, the first pin and the second pin are arranged to face each other in the swash plate chamber with the drive shaft in between.
In this compressor, when a pressure regulation valve is controlled to open, communication between the discharge chamber and the pressure regulation chamber is allowed, which raises the pressure in the control pressure chamber compared to the pressure in the swash plate chamber. This causes the non-rotational movable body and the movable body to proceed. Accordingly, the movable body causes the first arm of the swash plate to pivot about the first pin, while pushing the swash plate. At the same time, the lug arm causes the second arm of the swash plate to pivot about the second pin. That is, the movable body employs as a point of application the position of the first pin, at which the swash plate and the movable body are coupled to each other, and employs as a fulcrum the position of the second pin, at which the swash plate and the lug arm are coupled to each other, thereby causing the swash plate to pivot. In the compressor, the inclination angle of the swash plate is increased to increase the stroke of each piston, thus raising the displacement of the compressor per rotation cycle.
In contrast, by controlling the pressure regulation valve to close, the communication between the discharge chamber and the pressure regulation chamber is blocked. This lowers the pressure in the control pressure chamber to a level equal to the pressure level in the swash plate chamber, thus causing the non-rotational movable body and the movable body to retreat. Accordingly, in contrast to the case in which the inclination angle of the swash plate is increased, the non-rotational movable body and the movable body are moved rearward. Accordingly, the movable body causes the first arm of the swash plate to pivot about the first pin, while pulling the swash plate. At the same time, the lug arm causes the second arm of the swash plate to pivot about the second pin. The inclination angle of the swash plate is thus decreased and the piston stroke is decreased correspondingly in this compressor. This reduces the displacement of the compressor per rotation cycle.
In the compressor disclosed in Japanese Laid-Open Patent Publication No. 52-131204, an actuator is arranged in a swash plate chamber in a manner rotatable integrally with a drive shaft. Specifically, the actuator has a rotation body rotating integrally with the drive shaft. The interior of the rotation body accommodates a movable body, which moves in the direction of the rotation axis of the drive shaft and is movable relative to the rotation body. A control pressure chamber, which moves the movable body using the pressure in the control pressure chamber, is formed between the rotation body and the movable body. A communication passage, which communicates with the control pressure chamber, is formed in the drive shaft. A pressure control valve is arranged between the communication passage and a discharge chamber. The pressure control valve changes the pressure in the control pressure chamber to allow the movable body to move in the direction of the rotation axis relative to the rotation body. The rear end of the movable body is held in contact with a hinge ball. The hinge ball is arranged in a center of the swash plate and couples the swash plate to the drive shaft to allow the swash plate to pivot. A pressing spring, which urges the hinge ball in such a direction as to increase the inclination angle of the swash plate, is arranged at the rear end of the hinge ball.
A link mechanism includes the hinge ball and a link arranged between the rotation body and the swash plate. The hinge ball is urged by the pressing spring located behind the hinge ball to keep contacting the rotation body.
A first pin perpendicular to the rotation axis of the drive shaft is passed through the front end of the arm. The first pin couples the arm and the rotation body to each other, and the front end of the arm is allowed to pivot relative to the rotation body about the first pin. Also, a second pin perpendicular to the rotation axis of the drive shaft is passed through the rear end of the arm. The second pin couples the arm and the swash plate to each other, and the rear end of the arm is allowed to pivot relative to the swash plate about the second pin. In other words, the arm and the first and second pins couple the swash plate and the rotation body to each other.
In this compressor, when a pressure regulation valve is controlled to open, communication between the discharge chamber and the pressure regulation chamber is allowed, which raises the pressure in the control pressure chamber compared to the pressure in the swash plate chamber. Accordingly, the movable body retreats and pushes the hinge ball rearward against the urging force of the pressing spring. At this time, the arm pivots about the first and second pins. That is, the compressor employs as a point of application the position at which the movable body pushes the hinge ball, and employs as fulcrums the position at which the swash plate and the rotation body are coupled to each other, that is, the ends of the arm through which the first and second pins are passed through, thereby causing the swash plate to pivot. Accordingly, when the inclination angle of the swash plate is decreased, the piston stroke is decreased. This reduces the displacement of the compressor per rotation cycle.
In contrast, by controlling the pressure regulation valve to close, the communication between the discharge chamber and the pressure regulation chamber is blocked. This lowers the pressure in the control pressure chamber to a level equal to the pressure level in the swash plate chamber. Accordingly, the movable body proceeds, and the hinge ball is caused to follow the movable body by the urging force of the pressing spring. This causes the swash plate to pivot in a direction opposite to the direction in which the inclination angle of the swash plate is reduced, so that the inclination angle is increased. The stroke of the pistons is thus increased.
Swash plate type variable displacement compressors employing an actuator as described above are desired to have a higher controllability with regard to the displacement control.
In this respect, according to the compressor described in Japanese Laid-Open Patent Publication No. 5-172052, when the rotation body causes the movable body to proceed in the axial direction of the drive shaft via the thrust bearing, the thrust bearing may be deformed. This may result in an inefficient or slow transmission of force. As a result, the inclination angle of the swash plate may not be changed in a favorable manner, thus hampering desirable displacement control performed by selectively increasing and decreasing the piston stroke.
According to the compressor described in Japanese Laid-Open Patent Publication No. 52-131204, since the hinge ball is arranged in the center of the swash plate, the point of application at the time of changing the inclination angle of the swash plate is located in the vicinity of the center of the swash plate. Therefore, the point of application and the fulcrum are close to each other in this compressor. Thus, when the movable body of the compressor pushes the hinge ball, a great pressing force is required. This makes it difficult to change the inclination angle of the swash plate of the compressor in a favorable manner, thus hampering desirable displacement control.